1. Field of the Invention
The present invention relates to an ink composition, an ink set, and an image recording method.
2. Related Art
For color image recording materials, so-called subtractive three primary color dyes (dyes or pigments) and a black dye have been used to reproduce or record full color images. However, under the current circumstances, there is no dye with fastness having absorption properties capable of realizing preferable color reproduction regions and having resistance to various use conditions. Thus, improvement thereof has been strongly desired.
Ink jet recording methods have been rapidly popularized and are undergoing further development because the methods have advantages of low material costs, capability for high-speed recording, and low recording noise, and further allow color recording with ease.
The ink jet recording methods include continuous methods in which droplets are ejected in succession and on-demand methods in which droplets are ejected according to image information signals. In the ink jet recording methods, the droplets of an ink are discharged by a method of applying pressure to the ink by a piezo device; heating the ink to generate bubbles therein; using an ultrasonic wave; or aspirating the ink by an electrostatic force. As inks for ink jet recording, water-based inks, oil-based inks, or solid (melting-type) inks are used.
Colorants contained in the ink for ink jet recording are required to have excellent solubility or dispersibility in a solvent; to be capable of recording with a high density; to be excellent in hue; to have fastness with respect to light, heat, environmental active gases (e.g., SOx in addition to oxidizing gases such as NOx and ozone), water, and chemicals; to have excellent fixability with respect to an image receiving material and hardly blur; to be excellent in storability as an ink; to have no toxicity; to be high in purity; and to be available at a low price.
In order to satisfy these requirements, ink jet dyes have been vigorously developed which have fastness with respect to light, heat, and environmental active gases (e.g., Japanese Patent Application Laid-Open (JP-A) Nos. 2001-335714, 3-103484, 4-39365, and 2000-303009). Moreover, it is disclosed that fastness increases by the use of dyes having an oxidation potential nobler than 0.8 V (vs SCE) (e.g., JP-A No. 2004-331699).